Seal for controlled atmosphere muffle furnaces



2 Sheets-Sheet 1 VENTOR A.

ATTORNEYS:

P. M HULME SEAL FCR CONTROLLED ATMOSPHERE MUFFLE FURNACES Aug. 3o, 1949.

Filed April 24, 1945 Aug. 30, 1949. P. M. HULME 2,480,293

SEAL FOR CONTROLLED ATMOSPHERE MUFFLE FURNACS Filed April 24, 1945 z sheets-sheetv 2 y l. /Q/lNvEN-ron an L4/mw y @uw ATTORQEYS aannam. so, ma

2.4mm A simi.v roncon'raomap'amosrnaas -imprimall'llluvaiuts i.. g ramp 1u. unime, summa, conn., signor a;

Air Reduction Company, Incorporated, a l'cori porationofNewYork' f I I suman April u, i945,- serm No. 590,065.-

e claims.' (cieca-4o)- g This invention relates to controlled-atmos- 'y phere munie furnaces of the bell type in which the muiiie is lowered onto a base to enclose the material to be treated within a-heating compartment formed by the munie and the base, and is lifted from the base to Apermit removal ,of the material when the heat-treating operation is completed. More particularly, the invention relates to the sealing of such furnaces to make the muiile gas-tight. v

The usual method of sealing the munie loi such furnaces is to lower it onto a bed of sand, -but this only partlyv seals its bottom edge. Thereillustrated in titles-of the more expensive gases such as nitrogen. v

.A muiile furnace embodying the yinvention is the accompanying drawing, in

Whichi Fig. 1 is a transverse vertical section through v the furnace: v

fore, a continuous stream of control gas must be passed into the muiile during the entire. heat-` treating operatlon. This is wasteful vof gas and makes the use of gases having a highA nitrogen content prohibitive in most cases. vbecause of the expense per heat-treating operation."-'Further` more, the active ingredients of the control gas,-

."Fig. 2 is a portion of Fig. l, drawn to a larger scale to more clearly illustrate the detalls of the sealing means for the muille; and

Fig. 3 is a plan view of the furnace.

n The furnace represented in the drawing, exceptfor the muiile sealing means hereinafter described, is a standard bell-type'radiant tube furnace comprising an inner shell or muiile l and an outerv cover 2 of refractory material. The

such as CO, CO2. H2, and H2O, and various uncracked hydrocarbons, react `with the` steel lor v other materialv being heat-treated. and reactwith each other, and if fresh gas is constantlyfbeing passed into the muille, these reactions continue If the mule is tightlysealed, a single purge,

walls of the outer cover are spaced from the walls o f themuilie to provide the usual heating space 3 .towhich heat is supplied by radiant tubes represented at 4. 5

rThe muille and cover 2 are adapted to be f lowered, in accordance with conventional prac- `tice, onto a base plate 5 made of cast iron and `to occur throughout the. heat-treating operation.

followed by a single lling with' the, controlgas is suiiicient -for the lentire vheattreating opera-A tion. Not so much control gas is then necessary; more expensive gas such as one containing a high percentage of nitrogen can be used economically, and since the atmosphere is static the active ingredients of the gas will reachequilibrium early in the heat-treating operation and no more reactions with the steel or other material vwill take place because no more active .ingredients are being put into the furnace. -f

Efforts have already been madeto obtain ltight sealing on some types of heat-treating furnaces' by employing oil channels in which the loweredge of the muiile is immersed. or by employing lead `having a facing 6 of brick or other refractory ymaterial on which the inutile and refractory cover are supported.

The material to be heat treated, such as coiled lstrips of sheet steel or other material, is rep- `resented at M (Fig. 1). The material is placed on thegbase and then the muille and cover are lowered, so that the mue forms with the base 'a .closed heat-treating or heating compartment. The control gas is supplied to this compartment p through the usual piping, represented at l.

The sealing means for the munie, provided in accordance with this invention, comprises an external horizontal flange 8, of relatively thin material as shown, which is welded to the muiiie a short distance above its lower edge, as indicated at 9. The flange extends completely around the muiile as shown in Fig. 3 and projects outwardly seals. However, such liquid and semi-liquid seais have the disadvantage that they partly volatilize and add to the complications ofthe heat-treat ing atmosphere. f

The principal object ofl my invention is to pro- I vide a simple mechanical seal for y'the muiile'of a bell-type mumefurnace which is thoroughly'` gas-tight; which will eliminate' the above-men- -tioned disadvantages associated with the use of liquid or semi-liquid seals. or seals that are not completely eective: and which makes it pos-- sible to use a single nlling of control' gas for a from it beyond the walls of the refractory cover 2. [The base E-has a sealing portion extending completely around the refractory cover. 2. Preferably. this sealing portion comprises an upwardly projecting boss 'l0 (Figs. i'and 2)v which is spacedroutwardly from the walls of the refractory cover. The nange s on the muille projects outwardlyl over the sealing portion or boss i0 on the base and is adapted to be clamped to it with suitable sealing material clamped in between.

Preferably, the flange 8 has a downwardly projecting boss Il at its lower side which coincides with and lies over the boss I 0 on the base. The

heat-treating operation and to use, greater quan;v 66 seslingmaterial represented at itfand which may be a gasket of silicone rubber. or other suitable sealing substance, is positioned between the boss It on the base and the boss II on the horizontal flange l. The flange is clamped to the base by means of a number of manually operated clamps locatedat spaced points around the furnace. As best shown in Fig. 2, each clamp may comprise a rod Il which is pivoted at its lower end to a bracket I4 on the base, as shown at I5. The upper portion of the rod is adapted to be received in a slot I6 in the edge of the flange l. The rod has a threaded upper end, as shown at I'l, on which a hand clamping wheel Il rotates.

From the foregoing it will be seen that the portion of the horizontal flange extending beyond the wall of cover 2 forms upper and lower heatradiating surfaces, and the boss III extending upwardly from bas'e 5 forms inner and outer heatradiating surfaces. Additionally, bosses I and II between which the sealing gasket I2 is compressed are spaced an appreciable distance away from the wall of cover 2. As a result, gasket I2 is protected from excessive heat and therefore will not only have a longer effective life, but may be selected from an assortment of sealing materials which are preferable for the purpose, but not rods I3 to compress the sealing material I2 between the bosses on the mufiie flange and the base. A tight mechanicalseal is thus eiected, so` that when control gas is admitted through the piping 1 into the heating compartment within the muiiie, it cannot escape. At the end of the heat-treating operation, the clamping wheels 8 are turned on the rods I3 to release the clamps, and the rods I3 are swung outwardly about their pivots to permit the refractory cover and the muiiie to be lifted ofi the base, so that the treated material may be removed.

The invention may be applied to furnaces of other types than that illustrated so long as there is a shell or the like cooperating with a base to form a heat-treating compartment which is to be made gas-tight by means of a seal between the lower edge of the shell and the base.

I claim:

1. A controlled-atmosphere furnace comprising a shell, a base on which said shell is supported to form an enclosed heating compartment, a horizontal external flange on the shell near but spaced from its lower edge, extending completely around the shell and of a length such as to form effective upper and lower heat-radiating surfaces, said base having a sealing portion extending. completely around the shell over which said flange is adapted to project, sealing material between said fiange and said sealing portion of the base and spaced from said shell substantially by the lengthof said flange, and means for clamping said flange to said sealing portion on the base with the sealing material clampedin between.

2. A controlled-atmosphere furnace comprising v a shell, a base on which said shell is supported to form an enclosed heating compartment, a

horizontal external flange on the shell near but spaced from its lower edge, extending completely around the shell and of a length such as to form eilectivo upper and lower heat-radiating sui'- faces, said base having a sealing portion extending completely around the shell over which said ange is adapted to project, sealing material between said ilange and said sealing portion of the base and spaced from said shell substantially by the length of said flange, and clamping means adapted to be manually operated either to clamp said flange to said sealing portion on the base with the sealing material clamped in between or to unclamp such parts and permit lifting of the shell from the base.

3. A controlled-atmosphere furnace comprising a shell, a base on which said shell is supported to form an enclosed heating compartment. said base having an upwardly projecting boss extending completely around said shell and spaced externally from the walls thereof and having inner and outer heat-radiating surfaces, a horizontal external flange on the shell near its lower edge and extending completely around the shell and projecting outwardly over said boss on the base so as to form upper and lower heat-radiating surfaces, sealing material between said flange and said boss on the base, and means for detachably clamping said ilange to said boss on the base with the sealing material clamped in between.

4. A controlled atmosphere furnace comprising a shell, a, base on which said shell is supported to form an enclosed heating compartment, said base having an upwardly projecting boss extending completely around said shell and'spaced externally from the walls thereof and having inner and outer heat-radiating surfaces, a horizontal external flange on the shell near its lower edge and extending completely around the shell and projecting outwardly over said boss so as to form upper and lower heat-radiating surfaces. said ange having at its lower side a downwardly projecting boss adapted to lie over the boss on the base, sealing material between the boss on said flange and the boss on the base, and means for detachably clamping said bosses together with the sealing material clamped in between.

5. A controlled-atmosphere muille furnace comprising an inner muiiie, a base on which said muille is supported to form an enclosed heating compartment, a refractory cover supported on said base and enclosing the muiile, the walls of the cover being spaced from the walls of the muille to form a heating space, means for supplying heat to said heating space, said base having an upwardly extending boss outside of said cover, extending completely around the same and spaced therefrom to provide inner and outer heat-radiating surfaces, a horizontal external flange on the muille near its lower edge and extending completely around the muilie, said flange projecting outwardly beyond the refractory cover and over said boss on the base so as to form upper and lower heat-radiating surfaces, sealing material between said flange and said boss on' the base, and means for detachably clamping said munie flange to said boss on the base with the sealing material clamped in between.

6. A controlled-atmosphere muille furnace comprising an inner muiiie, a base on which said Y muiile is supported to form an enclosed heating extending completely around the same and spaced' therefrom so as to provide inner and outer heatradiating surfaces, a. horizontal external flange on the muiiie near its lower edge and extending completely around the munie, said flange projecting outwardly beyond the refractory cover and over said boss on the base so as to form upper and lower heat-radiating surfaces, a downwardly projecting boss on the lower side of said munie ange coinciding with and lying over the boss on the base, sealing material between the boss 10 on said ange and the boss on the base, and means for detachably clamping said bosses together with the sealing material clamped in between.

PHILIP M. HULME.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,427,319 Peacock Aug. 29, 1922 1,617,359 Westberg Feb. 15, 1927 1,892,112 Moore Dec. 27, 1932 2,050,029 Williams Aug. 4, 1936 2,169,404 Buttner Aug.l 15, 1939 Pfanstiehl Aug. 15, 1939 

